Recent efforts in research and development in the telecommunications industry have concentrated on establishing integrated voice and data within communication systems such as key telephone systems and PABXs. For example, the Kontact.TM. work station manufactured by Mitel Corporation, offers an integrated subscriber set and personal computer. Special features such as "dial-by-name" can be implemented by the Mitel device, along with standard personal computer features such as word processing, spread-sheet programs, etc. Also, data communication to outside telephone lines is implemented by means of an onboard modem.
Other integrated voice and data telephone sets are also well known. For example, U.S. Pat. No. 4,322,581 (Christain et al) discloses an integral voice and data set for use with common equipment in a telephone network. However, the system disclosed in Christain et al, as well as the above described Mitel device suffer from the disadvantage that each data set requires a dedicated microprocessor and associated peripheral circuitry, such as memory units, floppy disks, modems, etc. Hence, such prior art voice and data sets have been found to be expensive and of complex construction and design.
Additional voice and data systems are known in which both voice and data signals are transmitted in digital form and routed via sophisticated and expensive digital time/space crosspoint switches, and multiplex circuitry. Such systems are described for example in U.S. Pat. Nos. 4,160,131 (Kaul et al) and 4,627,046 (Bellamy), and elsewhere in numerous publications and articles relating to ISDN (Integrated System Digital Network) type systems.
While such prior integrated digital voice and data systems provide standard interfaces between various manufacturers as well as accurate and efficient performance, the circuitry required for implementing such systems is generally expensive and highly complex.
Other prior art systems are known which teach voice and data communication within a single system. For example, U.S. Pat. No. 4,440,986 (Thorson) relates to a microprocessor controller having a central processor for controlling a PBX and also separately controlling operation of a plurality of data terminals to provide a general computing capability. According to Thorson, the functions of PBX and data communications are separate and not integrated. In particular, the general computing function is defined as being unrelated to the operation of the telephone system.
Additional prior art of interest is disclosed in U.S. Pat. Nos. 4,096,359 (Barselotti); 4,140,885 (Varehagen) and 4,506,346 (Bennett et al).